This application is for renewal of a grant which has supported our research for a number of years and is related to the following areas: 1. The biliary excretion of steroids, primarily in human subjects with emphasis on the ensuing enterohepatic circulation. 2. The role the kidney plays in the conjugation and/or metabolism of certain steroids. 3. Further studies on the steroid protein interactions in human plasma and tissues. 4. Further characterization and purification of receptor proteins for estrogens present in the pancreas and prostate of the human and animals. 5. The utilization of antibodies against transcortin for the study of the biosynthesis of transcortin and the measurement of its concentrations in plasma and tissues. 6. Ultrastructural studies on the pathways taken by steroids in the liver in relation to their biliary excretion.